Spring ushers in a familiar icon in the skies

Posted on Wednesday, May 15, 2013 at 9:42 am

The warmer temperatures have brought with them some familiar Chesapeake icons. The osprey (Pandion haliaetus) occurs in nearly every corner of the globe, but nowhere as abundantly as on the Chesapeake Bay. These large brown and white birds of prey, with wingspans of 4-5 feet, return to the Bay and its many rivers and creeks every spring from southern wintering grounds.

Lured here by an abundance of food, they feed exclusively on live fish. Curved, sharp talons and rough-soled feet are designed to hold onto slippery fish. Ospreys soar over the water or hover on beating wings to scan for schooling or spawning fish. Upon sight of prey, an osprey folds its wings tightly, descends swiftly and plunges feet first into the water. Ospreys are also adept at scooping fish near the surface of the water.

The Chesapeake Bay provides excellent nesting areas near the water such as duck blinds, navigation markers, buoys or man-made nesting platforms. Offshore structures offer protection from predators, like raccoons, and rapid detection and escape from danger. On land, ospreys may nest in high trees or on utility poles.

Ospreys 3 years or older usually mate for life, and will use the same nest site year after year. A recently reunited pair will begin the task of nest building or repair. Spring courtship marks the beginning of a five-month period when the pair works together to raise their young.

A clutch of three or four eggs is laid by the third week of April. The sheer bulk of the nest and a depressed center conserves heat. The eggs, usually mottled cinnamon brown, are about the size of jumbo chicken eggs, and must be incubated for nearly five weeks.

Finally, the eggs yield their treasures: helpless chicks, weighing 2 ounces or less, that can barely beg for food. Amazingly, with plenty of fish, these balls of fluff will become soaring acrobats in just eight weeks.

By late July, most young Chesapeake ospreys are on the wing. By the end of August, both young and adults begin their southern migration to wintering grounds in the Caribbean, Central America and South America.

Ospreys, swooping and plunging for fish, have always been a familiar site for residents and visitors on the Chesapeake Bay. There was a time, not long ago, when their survival was threatened: They, like eagles and other birds of prey, were unable to produce enough young. Their eggshells had become extremely thin and broke before chicks could fully develop and hatch.

Years of research led to the discovery that a pesticide, known as DDT, caused eggshell thinning in many birds. The use of DDT was banned in the United States in the early 1970s. Since then, ospreys, bald eagles and birds of prey have made remarkable recoveries. Ospreys continue to flourish around the Bay, but they still face hazards.

Because they are very tolerant of people, ospreys will fish and nest close to populated communities. They often line their nests with a variety of natural and man-made materials. Some of these materials include paper, plastic, rope and fishing line.

Osprey chicks have been found entangled in fishing line or impaled with fishing hooks. Adults have also been spotted entangled in line. Legs, wings and beaks can become so tangled that the bird is not able to stand, fly or eat. Conservative estimates indicate that fishing line is present in 5-10 percent of all osprey nests on the Chesapeake Bay and surrounding rivers.

We can all help to reduce this threat to ospreys and other wildlife. If you are fishing, whether from a boat, pier or shoreline, retrieve any broken lines and drop them in a trash container. If none are available, take any discarded line, lures and hooks home and dispose of it there.

The resurgence of ospreys after the DDT ban is a success story. This success can extend to the entire Bay and other wildlife as we continue to protect and restore habitats.

Whether you’re fishing, sailing, boating, swimming or walking along a shoreline, chances are you will come across trash that can be harmful to birds and other wildlife. But each of us can help. Simply collect any abandoned fishing line and other trash — even if it’s not yours — and dispose of it properly. It’s a no-brainer.